The field of this invention relates to a polycondensation process for the manufacture of organic polymers from prepolymers or salts using a high temperature system wherein the polymerization is conducted in a steam or vapor stream at melt temperatures in the range of about 350.degree. F. to about 750.degree. F. while the wall temperature of the aerosol jet tube reactor is about 400.degree. F. to about 1000.degree. F. and the total residence time is kept in the range of about 0.1 seconds to about 20 seconds. Our process is suitable for the manufacture of polyesters, polycarbonates, polyarylates, polyesterarylates, polyamides, polyamide-imides and polyimides. Our novel aerojet regime process is applicable to any polycondensation reactor provided the salt or prepolymer is homogeneous and is in a single phase, the salt or prepolymer is stable under the high reaction temperatures and is capable of forming droplets. This means that the salt or prepolymers useful in our novel process atomize easily at the inlet of the jet reactor and thus have a high surface to volume ratio in the reactor.
Our novel aerosol jet process for the manufacture of polyamides, polyamide-imides, polyimides, polyesters, polycarbonates, polyarylates and polyesterarylates is unknown to the prior art, however, we will discuss the most relevant prior art references relating to polyamides.
U.S. Pat. No. 2,361,717 discloses a slug flow tubular reactor, reaction pressures were about 1000 psig in the preheat sections and residence times were 15 to 30 minutes. This is clearly a much slower process than our novel aerosol jet process where the residence times are about 0.1 to about 20 seconds. Another reference of interest may be Canadian Patent No. 527,473 which discloses the use of variable tube diameters to control pressure drop and temperatures. U.S. Pat. No. 3,960,820 discloses a slug flow regime using steam injection to control residence time by pressure control. Other references of interest include U.S. Pat No. 2,689,839 and U.S. Pat. No. 3,357,955 which relate to additive additions or product quality adjustment of polyamides; and U.S. Pat. No. 3,300,449 which discloses a residence time of about 10 to about 120 minutes. U.S. Pat. Nos. 3,193,535 and 3,258,313 disclose a process with a tubular reactor which uses a high water content 47% by weight. In reviewing all these references it is clear that our novel aerosol jet polycondensation process has not been contemplated by the prior art.
The general object of this invention is to provide a novel polycondensation process wherein the polycondensation is carried out in an aerosol jet regime at melt temperatures of about 500.degree. F. to about 750.degree. F. and contact times of about 0.1 seconds to about 20 seconds. A more particular object is to provide a novel condensation process for condensing aromatic carboxylic acids and anhydrides with diamines which are difficult to conduct under methods known to the prior art. Further, objects will be apparent from the description of the invention hereunder.
In our novel process we prepare a salt by reacting an aliphatic or aromatic diamine with di, tri or tetracarboxylic acids or their corresponding anhydrides or mixtures of the various acids or anhydrides. For polyesters, polycarbonates, polyarylates and polyesterarylates we prepare the appropriate prepolymers.
Suitably, in our process for the manufacture of polyamides, polyamide-imides or polyimides, a salt is first produced. This is carried out in any suitably designed stirred reactor. Feed materials are charged into the reactor at a temperature of about 75.degree. F. to about 175.degree. F. Solvent content of the salt solution is maintained at less than 25% by weight, preferably about 13 to about 17% by weight. Temperatures are then raised to provide a homogeneous salt solution. This is usually the range of about 375.degree. F. to about 450.degree. F. As quickly as possible, pressures are allowed to build to the limits of the equipment, usually to about 300 to about 600 psig. The salt prepared as described above is metered through a pump and pressure is increased to about 1500 to about 3000 psig. If additional processing is required to purify or filter the salt solution, the operation is carried out prior to the pump. The resulting salt and prepolymer mix is then heated and flashed through a control valve or nozzle to give an aerosol mist at pressures of about 0 to about 400 psig. The salt and prepolymer mix then is passed through the flash reactor. This reactor is designed to provide a high heat flux to the polymer and has a wall temperature of about 600.degree. F. to about 1000.degree. F. The melt temperature range is about 500.degree. F. to about 750.degree. F. through the flash reactor. The total residence time of the reactants in the flash reactor is about 0.1 to about 20 seconds, preferably about 0.2 to about 10 seconds and varies with the feed rate and pressure which are suitably in the range of about 100 lb/hour inch.sup.2 to about 200 lb/hour inch.sup.2.
In our process specific mass flow refers to mass flow per unit of reactor cross sectional area. The lower limit is defined by the limits of proper flow velocity through the reactor for the aerosol jet regime as opposed to slug flow. The upper limit is defined by the limits of heat input. When utilizing our process to prepare polyesters from dicarboxylate acids and glycol, polycarbonates from diphenols and phosgene, polyarylates from diphenols and dicarboxylic acids and polyesterarylates from diphenols, dicarboxylic acids and phosgenes we prepare a prepolymer which can suitably be an oligomer, dimer or trimer but must be homogeneous and is in a single phase, is stable under the high reaction temperatures and is capable of atomizing readily at the inlet of the jet reactor. The temperatures and other reaction conditions are the same as set forth hereinabove. Suitable polyesters which are prepared by our process and disclosed by Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley and Sons (1982), pages 531-576, including the references cited therein. All the pages and the references cited therein from the article in Kirk-Othmer are incorporated into this application and made part hereof. Suitable polycarbonates which are prepared by our process are disclosed in the aforementioned Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 18, pages 479 through 494 including the references cited therein and in Chapter 2 of the book, New Linear Polymers by Lee et al, McGraw Hill Book Co. (1967) including the references cited therein. All the pages from both citations are incorporated into this application and made part hereof including the references cited in the Kirk-Othmer article and in Chapter 2 of the Lee et al book. Suitable polyarylates prepared by our process are disclosed in U.S. Pat. Nos. 3,772,389 and 4,302,382 and the references cited therein. Both patents and the references cited therein are incorporated by references into this application and made part hereof.
Suitably, from the flash reactor the polymer is injected directly on to the screws of a twin screw extruder. Residence time in the twin screw extruder is about 45 seconds to about 3 minutes. Other types of finishing reactors are also suitably employed such as disc ring reactors, agitated stranding devolatizers and thin film evaporators.
The advantages of our novel aerosol jet reactor process are that the flow regime in the flash reactor is an aerosol jet and that the residence time after salt preparation is about 76 to about 240 seconds while in the prior art process the residence time is in the range of about 75 to 240 minutes. The maximum melt temperature in our novel process is about 620.degree. F. to about 730.degree. F. while in the prior art processes the range is below 570.degree. F., usually around 390.degree. F. to 450.degree. F. Furthermore, in our process the flow is self-controlling while the prior art processes require special controls. A further advantage of our novel aerosol jet process is that we are able to process high melt viscosity polymers while conventional processes are not able to process high melt viscosity polymers with any confidence.
Suitable di, tri and tetracarboxylic acids useful in our process to manufacture polyamides include terephthalic acid, isophthalic acid, trimellitic acid, 5-tertiary-butylisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, bussylic acid and etc. The preferred acids are terephthalic acid, isophthalic acid and adipic acid and mixtures of these.
Suitable anhydrides useful in our process include trimellitic anhydride, pyromellitic dianhydrides, 2, 3, 6, 7-naphthalene tetracarboxylic dianhydride, 3,3', 4,4'-diphenyl tetracarboxylic dianhydride, 1, 2, 5, 6-naphthalene tetracarboxylic dianhydride, 1, 2, 3, 4-cyclopentane tetracarboxylic dianhydride, 2,2', 3,3'-diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4-dicarboxyphenol sulfone dianhydride, 3, 4, 9, 10-perylene tetracarboxylic dianhydride, 2, 3, 4, 5-pyrrolidone tetracarboxylic dianhydride, bis(3,4-dicarboxylphenyl)ether dianhydride; ethylene tetracarboxylic dianhydrides; 3,3', 4,4'-benzophenone tetracarboxylic dianhydrides, bis(3,4-dicarboxylphenyl)sulfide dianhydride, bis(3, 4-dicarboxylphenyl)methane dianhydride, 1, 4, 5, 8-naphthalene tetracarboxylic dianhydride and etc. The preferred tricarboxylic acid anhydride is trimellitic anhydride. It should be understood that tricarboxylic acids and their corresponding anhydrides like trimellitic anhydride are useful for the manufacture of polyamide-imides and tetracarboxylic acids and their corresponding anhydrides are useful for the manufacture of polyimides.
Aliphatic, cycloaliphatic and aromatic diamines useful in our process include the following: hexamethylene diamines, trimethylhexamethylene diamine, ethylenediamine, tetramethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, dodecamethylene diamine, 4,4'-diamino(dicyclohexylmethane), xylene diamine. The preferred aliphatic diamines include hexamethylene diamine and trimethylhexamethylene diamines.
Suitable aromatic diamines useful in our process include para- and meta-phenylenediamine, para- and metaxylenediamine, para-toluenediamine, 2,4-toluenediamine, 2,6-toluenediamine, 3,5-toluenediamine, oxybis(aniline), thiobis(aniline,), sulfonylbis(aniline), diaminobenzophenone, methylenebis(aniline), benzidine, 1,5-diaminonaphthalene, oxybis(2-methylaniline), thiobis(2-methylaniline), and the like. Examples of other useful aromatic primary diamines are the following: 2,2'-naphthalene diamine, 2,4'-naphthalene diamine, 2,2'-biphenylene diamine, 3,3'-biphenylene diamine, 4,4'-biphenylene diamine, and the like; 3,3'-dichlorobenzidine, ethylene dianiline (4,4'-diaminodiphenyl ethane), and the like; ketodianiline, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, hexafluoroisopropylidene-bis(4-phenyl amine), 4,4'-diaminodiphenyl methane, 2,6-diaminopyridine, bis-(4-aminophenyl)-diethyl silane, bis(4-aminophenyl)ethyl phosphine oxide, bis(4-aminophenyl)-N-phenylamine, bis(4-amino-phenyl)-N-methylamine, 3,3'-dimethyl-4,4'-diaminobiphenyl para-bis(2-methyl-4-aminophenyl)-benzene, 3,3'-diaminoadamantane. The preferred aromatic diamine is meta-phenylene diamine.
The preferred process comprises preparing a salt of an aliphatic or aromatic diamine or a mixture of these and di, tri or tetracarboxylic acid, a mixture of these or their corresponding anhydrides by reacting both feedstocks at a temperature of about 375.degree. F. to about 450.degree. F. in an aqueous medium provided the water content of the resulting solution is kept below 25% water by weight. The resulting salt solution is subjected to a pressure of about 1500 to about 3000 psig and is then passed through a preheat zone where the temperature is increased from about 425.degree. F. to about 625.degree. F., the total residence time is kept about 25 to about 50 seconds, the reactants then are flashed through a control valve or nozzle to give an aerosol mist at a pressure of about 0 to about 400 and melt temperatures of about 500.degree. F. to about 750.degree. F. The total residence time in the reactor being about 0.1 to about 20 seconds. The polymer is then injected onto the screws of a twin screw reactor. The residence time in the extruder is about 45 seconds to about 3 minutes.
The preferred polymers manufactured by our process are the polyamides prepared from hexamethylene diamine and terephthalic acid, isophthalic acid and adipic acid in the mole ratio of about 100:65:25:10; to about 100:85:5:10; and the polyamides which are prepared from hexamethylene diamine, terephthalic acid and isophthalic acid in the mole ratio of about 100:30:70 to about 100:90:10.
These polyamides, polyamide-imides and polyimides prepared by the novel process described herein are used as replacements for metals in engineering applications, and therefore, they are molded and usually filled with reinforcing materials. For other applications fibers and laminates are also prepared from the polymers manufactured using our novel process.
Injection molding of the novel polymers produced by the novel process is accomplished by injecting the polymer into a mold maintained at a temperature of about 250.degree. F. to about 500.degree. F. In this process a 0.1-2.0 minute cycle is used with a barrel temperature of about 500.degree. F. to about 700.degree. F. The injection molding conditions are given in Table 1.
TABLE 1 ______________________________________ Mold Temperature 250-580.degree. F. Injection Pressure 2,000 to 40,000 psi and held for 0.5-20 seconds Back Pressure 0-400 psi Cycle Time 6-120 seconds Extruder Nozzle Temperature 500.degree. F. to 700.degree. F. Barrel Temperature 500.degree. F. to 700.degree. F. Screw 10-20 revolutions/minute ______________________________________
We have found that the novel polyamides , polyamideimides and polyimides prepared by our novel process are improved by the addition of reinforcing material, particularly the mechanical properties of the polymers are improved if these polymers contain from about 10 to about 60% by weight glass fibers, glass beads, or graphite or mixtures thereof. The preferred range is about 30 to about 40%. Suitable reinforcing materials are glass fibers, glass beads, glass spheres and glass fabrics. The glass fibers are made of alkali-free boron-silicate glass or alkali containing C-glass. The thickness of the glass fiber is suitably on the average between 3 mm and 30 mm. The length of the glass fiber is not critical and both long and short glass fibers are suitable. Long fibers have an average length of from 5 mm to 55 mm and short fibers have an average filament length from about 0.05 mm to about 5 mm. Any standard commercial-grade fibers, especially glass fiber, may be used to reinforce our polymers. Glass beads ranging from about 5 mm to about 50 mm in diameter may also be used as a reinforcing material.
The reinforced polymers may be prepared in various ways. For example, so-called roving endless glass fiber strands are coated with the polymer and subsequently granulated. The cut fibers or the glass beads may also be mixed with the soluble polymer and heated to form the reinforced polymer. Injection molding of the reinforced polymers is carried out in the same manner as shown in Table 1.
The following examples illustrate the preferred embodiments of the invention. It will be understood that the examples are for illustrative purposes only and do not purport to be wholly definitive with respect to conditions or scope of the invention.